Multistage centrifugal pumps



July 9, 1968 v. VQMOLA MULTISTAGE CENTRIFUGAL PUMP Filed Aug. 22. 1966 Illl/ r Y I d Kaza/ay yyi'mo/a INVENTOR.

United States Patent O 3,391,642 MULTISTAGE CENTRIFUGAL PUMPS Vclav Vymola, Smrzice, Czechoslovakia, assignor to Sigma, narodni podnik, Lutin, Czechoslovakia Filed Aug. 22, 1966, Ser. No. 573,986 Claims priority, application Czechoslovakia, Aug. 23, 1965, 5,210/65 10 Claims. (Cl. 10S-97) ABSTRACT F THE DISCLOSURE A multistage centrifugal pump having suction control `has a series of impellers which, with the exception of the first impeller that is nearest to the inlet, are fixed to the drive shaft, the first impeller being freely rotatable about the drive shaft. Fixedly connected with this first impeller is a driving turbine runner, and a means is provided for supplying pressure liquid to the turbine runner as well as for removing liquid therefrom, so that through the turbine runner the first freely rotatable impeller can turn relative to the drive shaft, and the succeeding impellers which are fixed thereto, for controlling the suction.

This invention relates to multistage centrifugal pumps and more particularly to centirfugal pumps with control of the suction capacity.

At present, multistage centrifugal pumps for pumping liquids where the static pressure on the suction side approaches the saturated vapour tensions are designed so as to prevent cavitation. This can be attained mainly by enlarging the inlet for the iirst stage impeller, or by injection of rather cool liquid into the suction space. IIn other cases, an independent priming pump with lower r.p.m. number is arranged in front of the condensateextraction pumps. Said designs are disadvantageous name ly because they make the dimensions of pumping aggregates larger and their use is, in many cases, reduced to relatively small capacities. In addition to condensate-extraction pumps another design is known in which the first impeller is pivoted on a shaft and driven by a hollow shaft mounted on said main shaft by means of a gear transmission with toothed wheels. Said gear transmission is mounted outside the hydraulic space. Said arrangement is rather complicated from the construction point of View. [It requires a precise manufacture of gears and does not enable the control of the suction capacity and the output of the pump.

It is an object of this invention to provide multistage centrifugal pumps which may attain a high suction capacity with the possibility of a suction control and which would be suitable even for high output capacities whereby the complicated and exacting additional device enlarging the pump dimensions and increasing the production costs would be eliminated.

The invention resides substantially in that the multistage centrifugal pump is provided with a first stage suction impeller freely turning on the pump shaft, said rst stage suction impeller connected to a `driving turbine runner.

According to another feature the driving turbine runner is driven by the pumped liquid supplied by Way of a diffuser by an additional pump impeller keyed on the pump shaft.

3,391,642 Patented .July 9, 1968 ICC The invention resides fur-ther in that the diffuser is provided with `means 4of a controlling pressure, direction and the amount of the driving liquid for the turbine runner for example by adjustable blades.

According to another alternative the turbine runner is driven by the pressure liquid from some foreign source passing through a distributor and through control means adjusting the pressure, direction and amount of said pressure liquid.

The invention resides further in that the first stage impeller pivoted on the pump shaft is designed as a double impeller having one inlet and two outlets..

The invention resides finally in `that the suction space of the additional pump impeller is interconnected by means of circulation piping with some of the pressure spaces of the pump stages.

Examples of pumps according to this invention are illustrated in the attached drawing. FIG.. l shows an arrangement with a driving turbine runner cooperating with an additional pump impeller and with a control member. FIG. 2 illustrates a similar arrangement wherein the driving turbine runner is driven by the liquid from a foreign source.

The multistage centrifugal pump according to this invention comprises a casing 13 defining a cavity and capable to hold a liquid. The casing 13 is provided with a suction inlet 24 and with a discharge outlet 28. An impeller driving shaft 14 driven from a not shown engine is rotatably mounted in said casing 13 in bearings 18, 19, the hydraulic space sealed by stuiiing boxes 20, 21. A number of axially spaced impellers is supported by the impeller driving shaft 14, the `first of said impellers 15 closest to the suction inlet 24 and cooperating therewith being freely rotatable on the impeller driving shaft 1'4, the remaining pump impellers 11 keyed on the shaft 14. Coaxially stacked, to the casing 13 peripherally abutting interstage diaphragms 12 are provided between said impellers 15 and 11, said diaphragms 12 supporting diffuser elements 29 passing the liquid to the subsequent impeller stage. The first impeller 15 is connected to a driving turbine runner 16 equally freely rotating around the impeller driving shaft 14. The first stage impeller 15 and the driving turbine runner 16 can be for instance connected by bolts or by mounting on its hub or both impeller 1'5 and runner 16 can be made as one unit. On the shaft 14 an additional impeller A17 is further keyed in front of said driving turbine runner 16. A diffuser 22 connects the outlet of the pump impeller 17 with the inlet of the driving turbine runner 16. The driving turbine runner 16, the additional impeller 17 and the diffuser element 22 form thus a substantially closed circuit, circulating a certain amount of liquid. It is advantageous to provide said diffuser 22 with a control member 23 of known design, which adjusts the parameters of the driving liquid entering the turbine runner 16, as pressure, direction and amount of the pressure liquid. By means of the casing 13 the diffuser 22 is connected with the other parts of the pump and forms with them a compact unit. One lor more channels 25 connect the space of the impeller 415 with the space of the driving turbine runner 16.

Before starting the pump the cavity of the casing 13 should be filled with the pumped liquid. Said liquid fills both the spaces of the proper pump and the spaces of driving turbine runner `16, of pump impeller 17 and diffuser 22 as well. The liquid enters said spaces through the channel or channels 25 interconnecting the space of suction inlet 24 or the space of the first stage suction impeller with the driving turbine runner 16. When the pump shaft 14 starts to rotate, simultaneously the pump impeller 17 runs at the same number of r.p.m. Said pump impeller 17 supplies pressure liquid through the diffuser 22 into the driving turbine runner 16 and causes it to run at a lower speed. Simultaneously with the driving turbine runner 16 also the first stage suction impeller 15 rotates at the same speed, sucking the pumped liquid and conveying it to the other stages. By the lower rpm. of the first stage suction impeller 15, a high suction capacity is attained and cavitation is prevented. If the pump according to this invention is used as a condensate-extraction pump, then the variable condition of the liquid level in the condenser requires adjustment of the suction capacity of the pump. This can be attained by means of changing the r.p.m. number of the first stage suction irnpeller 15. For that reason, the control element 23 controlling the pressure, `direction and amount of the driving liquid is mounted in the diffuser 22 in front of the inlet of the driving turbine runner 16. It is advantageous to provide said control element 23 with adjustable blades which in accordance with variations of the condenser level, are appropriately adjusted for the most suitable speed, direction, pressure and amount of the fiowing liquid. Thus the speed of the driving turbine runner i16 is adjusted and, at the same time, the speed of the first stage suction impeller 15 which further alter the suction capacity and the total output of the pump. in case the control element is arranged in some different manner, its control has to be properly arranged so as to respond to differences of the condenser level.

Within the substantially closed hydraulic circuit represented by the pump impeller 17, diffuser 22 and driving turbine runner 16, an increase of temperature of the liquid due to friction may occur. It is therefore advisable to provide for a circulation or for the cooling of the circulated liquid for instance by providing an external supply of liquid from one of the pressure stages of the pump by way of the circulation piping 26. The pumped liquid is conveyed from a pressure stage through said circulation piping 26 to the suction space of the pump impeller 17 and is drained through a channel or channels from the suction space of the driving turbine runner 16 to the space of the suction inlet 2d of the pump. The amount of circulating liquid can be controlled, if required, for instance by means of the valve 30. The device according to this invention can be also arranged as shown in FIG. 2 in such a manner that the driving turbine runner 16 is made to rotate by means of pressure liquid from some foreign source or from the outlet of the pump or from some of its stages. In that case the additional pump impeller 17 is not necessary and the diffuser acts as a distributor 27. The liquid is discharged from the turbine runner by way of the discharge outlet 31. If a closed circuit is used, the pressure liquid should pass an appropriate cooling device.

Compared with the present state, this invention represents a step forward in the construction of condensateextraction pumps for greater capacity than at present. Another advantage is that the pump can be designed as a single piece assembly having relatively low weight and dimensions because it is possible to use high velocities of the delivery stages and a controlled low velocity of the suction stage. Owing to the above mentioned facts, a high andadjustable suction capacity is provided with the possibility of appropriate accommodation of the pump to the operating conditions as well. In addition, the arrangement of the pump is relatively simple with low requirements upon production.

I claim:

1. Multistage centrifugal pump comprising a casing defining a cavity and capable to hold a liquid, a suction inlet and discharge outlet provided in said casing, an impeller driving shaft rotatable mounted in said casing,

a number of axially spaced impellers acting in series supported by said shaft, increasing progressively the pressure of the pumped liquid, the rst of said impellers closest to the suction inlet freely rotatable on said shaft, the remaining impellers fixed on said shaft, each impeller having an inner central inlet and an outer peripheral outlet, said casing provided with coaxially stacked peripherally abutting interstage diaphragms between said impellers, said interstage diaphragms supporting diffuser elements passing liquid from one impeller stage to the subsequent one, a driving turbine ruimer coaxial with said impellers and rfixedly connected to said first impeller which is freely rotatable on said impeller driving shaft, said driving turbine runner having an outer peripheral inlet and a central inner outlet so that liquid fiows therethrough radially in a direction opposite to the direction of liquid fiow through said impellers, means for supplying pressure liquid to said outer peripheral inlet of said turbine runner and means for removal of said liquid from said inner central outlet thereof, and means for sealing the impeller driving shaft mounted in said casing.

2. Multistage centrifugal pump comprising a casing defining a cavity and capable to hold a liquid, a suction inlet and a discharge outlet provided in said casing, an impeller driving shaft rotatably mounted in said casing, a number of axially spaced impellers acting in series supported by said shaft, increasing progressively the pressure of the pumped liquid, the first of said impellers closest to the suction inlet freely rotatable on said shaft, the remaining impellers fixed on said shaft, said casing provided with coaxially stacked peripherally abutting interstage diaphragrns between said impellers, said interstage diaphragms supporting diffuser elements passing liquid from one impeller stage to the subsequent one, a driving turbine runner coaxial with sai-d impellers connected to said first impeller freely rotatable on said impeller driving shaft, means for supply pressure liquid to said turbine runner, means for removal of said liquid therefrom, and means for sealing the impeller driving shaft mounted in said casing, the first stage impeller closest to the suction inlet arranged as twin impeller with one inlet cooperating with the suction inlet and with two outlets.

3. Multistage centrifugal pump as in claim y1, said driving turbine runner supplied with pressure liquid from an external source.

4. Multistage centrifugal pump as in claim 1, an additional impeller fixed to said shaft, said driving turbine runner supplied with pressure liquid from said additional impeller.

5. Multistage centrifugal pump as in claim 1 with means for adjustment of the parameters of the pressure liquid supplied to said driving turbine runner.

6. Multistage centrifugal pump comprising a casing defining a cavity and capable to hold a liquid, a suction inlet `and a discharge outlet provided in said casing, an impeller driving shaft rotatably mounted in said casing, a number of axially spaced impellers acting in series supported by said shaft, increasing progressively the pressure of the pumped liquid, the first of said impellers closest to the suction inlet freely rotatable on said shaft, the remaining impellers fixed on said shaft, said casing provided with coaxially stacked peripherally abutting interstage diaphragms between said impellers, said interstage diaphragms supporting diffuser elements passing liquid from one impeller stage to the subsequent/one, a driving turbine runner coaxial with said impellers connected to said first impeller freely rotatable on said impeller driving shaft, means for supplying pressure liquid to said turbine runner, means for removal of said liquid therefrom, means for sealing the impeller driving shaft mounted in said casing, and an additional pump impeller inside said casing, fixed to said impeller shaft and supplying pressure liquid to said driving turbine runner.

'7. Multistage centrifugal pump as in claim 6 provided with diffuser elements passing pressure liquid from said additional pump impeller to said driving turbine runner.

8. Multistage centrifugal pump as in claim 6 provided with means for adjustment of the parameters of the pressure liquid supplied by said additional pump impeller to said driving turbine runner, forming thus a substantially closed circuit.

9. `Multistage centrifugal pump as in claim 8 with means for supplying and means `for withdrawing a certain amount of liquid from said substantially closed circuit for cooling purposes.

`1t). Multstage centrifugal pump -as in claim 9 with lmeans for adjustment of the amount of liquid supplied and withdrawn from said substantially closed circuit.

6 References Cited UNITED STATES PATENTS 921,118 '5/1909 Kasley u 1013-98 1,089,248 3/1914 Michell 1013-98 2,349,731 5/1944 Hornschuch 10B-98 FOREIGN PATENTS 59,665 2/ 1947 Netherlands.

ROBERT M. WALKER, Primary Examiner.

LAURENCE V. EFNER, DONLEY I STOCKING,

Examiners. 

